Surface Modification Of NiTi By TiN Ceramic And Study Of Biocompatibility

Biocompatibility of NiTi alloy is good and NiTi alloy is widely applied in cardio-vascular system, urinary system, hepatobiliary system, trachea narrow or soften , collapse, and reproductive system and department of ophthalmology, but NiTi alloy has a lot of less than satisfactory place in hardness, corrosion resistance, and dissolvability of nickel ion etc. Titanium nitride ceramic thin film is deposited on NiTi by magnetron sputtering in expectation of improving the performance of NiTi.In this paper, the mechanical and tribological properties of the thin films, including nanohardness, wear resistance and friction coefficient and dissolvability of nickel ion and so on were measured, at last, we evaluated the biocompatibility of this material. Microstructures and microscopic appearance of thin films were characterized by X-ray photoemission spectroscopy(XPS) and scanning electron microscope (SEM);microhardness was tested by nano hardness tester;we used electrochemistry to examine the anti-corrosive performance of the material and its coating in Hank's, and we used the ICP-AES to determine the dissolvability of nickel ion of the material and its the coating in Hank's. Finally, the biocompatibility of NiTi alloy and TiN thin films were studied with fibroblast and osteoblast and vessel smooth muscle cell etc. Basic features of the cells, such as cell proliferation, cell viability and cell morphology were observed.Nanohardness of TiN thin films were 4.44 times higher than that of NiTi alloy. The nanohardness of NiTi is about 6.5217GPa but the TiN thin films is about 28.9855Gpa.Friction coefficient of TiN thin films is 0.93 and NiTi alloy is 0.62, this indicated that the surface roughness of the film sample is bigger than the original basis, which is more suitable for the growth of cells.The result of SEM proved conclusion described above, intensive protrudingparticles can be observed in the film under visual field of 1000 times, under the same multiple of enlarging, we can only observe smooth surface in the original basis.XPS analysis shows that there is nitrogen element on the film after magnetron sputtering, and there is not nickel element on it.ICP—AES analysis shows that the film can effectively prevent the nickel ion dissolving from the surface of NiTi alloy.Tafel plot and cyclic voltammetry plot were performed in Hank's simulated human plasma at 37°C. Results show that TiN thin film exhibit better corrosion protection than that of NiTi.In the evaluation of biocompatibility, all kinds of cells grow well on both materials, but the cell proliferation, cell viability and cell morphology on the TiN film are superior to the original basis.The result of this paper demonstrates some improvement of the physical surface properties under our experimental condition. The effects of these treatments on the biocompatibility have been well evaluated and assessed. Furthermore, it also gives important experimental data for developing and accelerating the clinical applications.